(1) Field of the Invention
The present invention relates to a system for installing cable in a conduit, and deals more particularly with an apparatus in the form of a cable flushing lateral for improving passage of a towed array cable through a guide tube of a submarine.
(2) Description of the Prior Art
When deploying a towed array from a submarine, the towed array cable passes from a capstan within the submarine through a guide tube, or conduit, which communicates with the medium surrounding the submarine. The capstan pushes the towed array cable through the guide as the cable is payed out. To lower the frictional forces of the cable against the interior of the conduit, water is pumped into the guide tube in the direction in which the cable is payed out. The water inlet to the guide tube consists essentially of an angled T-fitting. The water flowing past the cable creates a drag on the cable and assists in pulling the cable through the conduit. However, the force of the water entering the T-fitting occasionally pushes the cable against the opposite side of the conduit causing the cable to hang up within the conduit. Additionally, some of the water entering the T-fitting is directed opposite the direction of cable travel, resulting in drag forces opposing cable pay out.
Other methods for assisting in passing a cable through a conduit are well known in the art. Kunze et al., U.S. Pat. No. 5,011,332, disclose the use of various cable profiles to produce turbulence which in turn promotes the movement of the cable within the conduit. The profiles essentially consist of radial projections extending from the cable jacket or channels cut into the jacket. Still other methods known in the art utilize drocjues or pigs attached to the end of the cable as in U.S. Pat. No. 4,856,937 to Grocott et al. and U.S. Pat. No. 4,185,809 to Jonnes. Fluid pressure against the drogue or pigs pulls the cable through the conduit. When the cable emerges from the end of the conduit, the drogue or pig is removed and the remainder of the cable can be drawn through the conduit. Such systems would be helpful in conveying the end of the towed array to the point of exit from the conduit but would provide no additional assistance to the continued pay out of the towed array beyond this point. Changing the profile of the towed array or adding drogues or pigs to the array would result in additional costs required to retrofit the towed array or the array handling equipment. Moreover, the increased drag, turbulence and noise that both these methods generate are counter productive to the function and purpose of a towed sonar array.